code: def test_empty_references_and_hypothesis(self):
      # Test case where both references and hypothesis is empty.
      references = [[]]
      hypothesis = []
      assert sentence_bleu(references, hypothesis) == 0
  
imports: import unittest
  import numpy
  from nltk.data import find
  from nltk.translate.bleu_score import SmoothingFunction, brevity_penalty, closest_ref_length, corpus_bleu, modified_precision, sentence_bleu
label_desc: Use image node_id 5 for calling the TestBLEUFringeCases obj's underlying member method code with example usage: obj.test_empty_references_and_hypothesis() without return types